Breast Cancer Study Downplays Chemical Link

As reported in USA TODAY (30/10/97) by Steve Sternberg, a study from the Harvard Medical School, just published in the New England Journal of Medicine, claims that exposure to toxic pesticides and industrial chemicals does not appear to raise a women's risk of breast cancer.

According to the article in US TODAY, "The research casts doubt on the theory that exposure to environmental estrogens - such as those found in the pesticide DDT and in the multipurpose chemicals known as PCBs - has contributed to the rise in the nation's breast cancer rate."

Environmental estrogens can be either natural or man made chemicals that mimic or block the action of the human hormone estrogen. It has been well established from both animal and human studies that estrogen acts as a promoter of breast cancer.

This is true regardless of whether the estrogen is from a woman's ovaries or from a hormone pill. There is also the possibility that environmental estrogens from pesticides and industrial chemicals also have this same promotional effect.

However, as reported in the publication, Our Stolen Future , there are dangers from focusing to narrowly on the estrogen factor, warns Linda Birnbaum, head of the U.S. Environmental Protection Agency's Health Effects Research Laboratory.

"Estrogen is just one component in the complicated, integrated endocrine system, and, she says, synthetic chemicals target other parts of the system more commonly than they disrupt processes involving estrogen. The adrenal glands, which produce stress hormones, get hit more than any other organ by man-made compounds, followed by the thyroid gland.

Insults in any part of one system tend to quickly ripple through other systems of the body as well. So while breast cancer could be linked to estrogenic pesticides, it could also be linked to other kinds of hormone disruption. Birnbaum notes, for example, that depressed thyroid levels have been linked to breast cancer just as increased estrogen exposure has."(1)

In this study, which is the first of several major studies now under way, David Hunter of the Harvard Medical School and co-workers examined stored blood samples from 32,000 women in Harvard's Nurses Health Study. The researchers focused on 240 of the nurses who had later developed breast cancer and a control group of 240 nurses who did not later develop cancer.

The researchers tested the blood samples for traces of PCBs and DDE, a by-product of DDT metabolism. According to the researchers, women without breast cancer were the ones with higher levels of these chemicals.

"We found no evidence of a positive association between high levels of plasma DDE or PCBs and a risk of breast cancer." Hunter reported in the NEJM. "At this point," Hunter added, "the weight of the evidence indicates that it is unlikely that these compounds cause breast cancer."

 

Comment.

The concept of the Harvard Medical School study is straight forward; to see if breast cancer patients had higher levels of PCBs and the DDT byproduct DDE. If higher levels were found then we would have convincing evidence of a strong link between breast cancer and pesticide/chemical use.

However just because an obvious link was not found does not mean that there is not a link and that should have been pointed out by the researchers.

The fact is that practically all of us in the industralised countries have varying levels of chemical pollutants in our bodies but at the same time we all have differing genetic predispositions to developing cancer. It is widely accepted that there is a genetic link with some cases of breast cancer but most importantly, it appears to be an environmental risk factor which 'triggers' it off.

According to testimony from the First World Conference on Breast Cancer, held in Kingston, Ontario, Canada, in July of this year, up to 80 percent of breast cancer cases may be due to environmental pollutants.

Therefore it would be fair to say that one's level of man made chemical compounds and the likelihood of developing breast cancer is very much dependent on genetic factors, or to put it differently, it is dependent upon our individual genetic ability to tolerate these chemicals. As such, in breast cancer patients, their pesticide/chemical levels would not necessarily need to be elevated in order to be an initiater of breast cancer. If this is the case, then any study which only looks at these chemical levels, would most likely fail to find a connection.

A good analogy would be asbestos. There have been cases of asbestosis being caused by a brief exposure to asbestos, whereas many workers who have had extended exposures have not developed the disease long after the expected latency period. From this we can conclude that there is also another factor to consider than just a level of exposure.

Considering this, for the authors of this study to conclude that "it is unlikely that these compounds cause breast cancer", simply cannot be justified.

It is concerning to note that Gwen Collman the study's administrator at the National Institute of Environmental Health Sciences, states that if the further studies fails to find a link between chemical exposure and breast cancer, "we can say we've answered that question, and do research in other areas."

It is of concern that this preliminary study will probably now be used by the petrochemical industry as evidence that their products are 'safe', in much the same way as the unrelated National Cancer Institute's Linet study (as reported in the last issue of Electromagnetic Forum ) is now being used by the power industry as proof that powerlines electromagnetic fields do not cause cancer.

In the Linet study, the authors concluded that "Children exposed to electromagnetic fields by living near electrical power lines are not more susceptible to developing leukemia." In fact the authors could only come to this conclusion by excluding higher exposures which DID find a significant correlation. They were able to do this by using a cut-off point, below which one would reasonably expect not to find a connection.

The main conclusion I can draw from the Linet study is that it's parameters are conveniently designed to miminise a possible connection between powerline EMFs and childhood leukemia. (2)

With the pesticide/chemical issue, if further down the track we find that the thousands of man made chemicals now in our environment amazingly are not associated with the increase in breast cancer incidence, than what another environmental pollutant may be the culprit for the continuing rapid rate of increase?

The European Parliament may have shed some light that question back in March 1992 in a resolution which stated:

"Thus in the frequency range 100KHz to 300 GHz, 50 years ago it was scarcely possible to measure 10pW/cm2 on the ground in our countries. Today, depending on the location, values one million to one thousand million times higher are recorded because of the explosion of telecommunications. In the microwave range, the widespread use of the mobile phone, which involves the whole territory of the industrialised countries, will mean increased exposure.

Finally, in the case of low frequencies (powerline frequency), the multiple uses of electricity and the centralisation of its production, together with work on screens (computer monitors), are subjecting an increasingly sizable proportion of the population to high electromagnetic fields."

As mentioned on page 12 of this issue, research indicates that breast cancer tissue may be especially affected from exposure to radiofre-quency and microwave radiation and also that, in a joint statement from several Australian government departments, it is admitted, "Laboratory studies on animals suggest that where cancer exists, radio waves may accelerate its growth."

Interestingly, it is the industrialised countries that have the greatest increases in breast cancer, with an apparent strong correlation with increasing electromagnetic exposures and breast cancer incidence. The USA. currently has the highest in the world with 1 in 8 women expected to contract this disease during their lifetime.

In conclusion we must consider the liklyhood that no one factor will ever be found in isolation to be connected with the increasing incidence of this disease. In today's world we have an increasingly complex environmental mix of both chemical and electromagnetic pollution. It is known that combinations of chemicals can be far more toxic than each one in isolation. Evidence also indicates that the presence of electromagnetic fields can increase the toxicidity of chemicals.

It is unfortunate that in a time of cutting back on environmental laws, exempting industries from these laws with increasing talk of risk-benefit considerations and cost effectiveness methods, polluting industries who only consider corporate profits and governments with their main priority on the national economy are all to ready to uncritically accept scientific studies which fail to find adverse effects and yet all to ready to reject those studies that do find a connection.

References:

(1) Our Stolen Future : How Man-made Chemicals are Threatening our Fertility, Intelligence and Survival, Theo Colborn, John Peterson Myers and Dianne Dumanoski, Little, Brown and Company, 1996.

 

(2) ELECTROMAGNETICS Forum

Volume 1, No.3, Winter 1997, pages 1-4.